Abstract

We formalize within the percolation scheme that operates along the linear chain approximation, i.e., at one dimension (1D), an intrinsic ability behind Raman scattering to achieve a quantitative insight into local clustering/anticlustering in an alloy, using GeSi as a case study. For doing so, we derive general expressions of the individual fractions of the six GeSi percolation-type oscillators [1(Ge-Ge), 3(Ge-Si), 2(Si-Si)], which monitor directly the Raman intensities, via a relevant order parameter . This is introduced by adapting to the 1D oscillators of the GeSi-diamond version of the 1D-percolation scheme, i.e., along a fully consistent 1D treatment, the approach originally used by Verleur and Barker for the three-dimensional (3D) oscillators of their 1D-cluster scheme applying to zincblende alloys [H. W. Verleur and A. S. Barker, Phys. Rev. 149, 715 (1966)], a somehow problematic one in fact, due to its 3D–1D ambivalence. Predictive -dependent intensity-interplays between the Ge0.5Si0.5 Raman lines are confronted with existing experimental data and with ab initioRaman spectra obtained by using (32-atom) disordered supercells matching the required values, with special attention to the Ge-Si triplet and to the Si-Si doublet, respectively.

Received 19 April 2013Accepted 24 June 2013Published online 17 July 2013

Acknowledgments:

We are grateful to A. V. Postnikov for a critical reading of the manuscript and many useful discussions, and also to M. I. Alonso for stimulating our interest on clustering/anticlustering issues in GeSi. This work was supported by the European funding of Region Lorraine under Project FEDER-Percalloy No. presage 34619. V.J.B.T. would like to thank for funding by the Fundação para a Ciência e a Tecnologia, Portugal (FCT) under the Grant PEst-C/CTM/LA0025/2011.